A 17.5% annualized dividend growth rate over the past five years for insurer Aflac (AFL) ranks as sixth best among S&P’s Dividend Aristocrats -- the 51 companies within the S&P 500 that have managed annual dividend increases for at least 25 years.

This is part of series on the 10 Dividend Aristocrats with the highest dividend growth. Links to previous articles are below. Previous dividend growth articles in the series have featured Clorox (CLX), T. Rowe Price (TROM), Wal-Mart (WMT) and Medtronic (MDT).

For value investors, Aflac -- which sells insurance in the U.S. and Japan -- has the lowest PE ratio in our top 10; its 8.8 PE is 40% lower than the S&P 500 average. Aflac is rated Attractive by YCharts’ proprietary valuation model. Target (TGT) is the only other of our Top 10 Aristocrat dividend growers to carry an Attractive rating right now.

Now as is usually the case, a basement level PE signals a dragging stock. Indeed, the past five years haven’t been stellar, as seen in a stock chart.

Indeed, revenue in Japan increased 10% in the third quarter. Management said it expects 2012 new premium sales in Japan to rise 30% to 35% from a year earlier. While revenue growth is a big factor in the recent bump in the stock’s price, so too is continued improvement in its investment portfolio. The insurer was sitting on a ton of European bank and debt investments right about when the Eurozone started its periodic economic freak-outs. A new chief investment officer, from Goldman Sachs (GS), arrived in 2011 and has been aggressively reworking the $110 billion portfolio. Unrealized losses from investments have declined from $3 billion in 2009 to $1.3 billion at the end of the third quarter.

One looming wildcard is the pending privatization of the state-run Japan Post, with an expected transition date of late 2015. In Japan, most insurance is sold through the postal service (it has a bank and an insurance arm.) Cancer insurance is a popular product in Japan, and Aflac has a 70% market share stranglehold. If the newly privatized entity decides to roll out proprietary insurance products that could impact an important distribution channel for Aflac.

What’s not in question is the reliability of the dividend. The payout ratio is near 20% and the cash payout ratio is below 10%. Aflac’s current dividend yield is 2.7%.

Carla Fried, a senior contributing editor at ycharts.com, has covered investing for more than 25 years. Her work appears in The New York Times, Bloomberg.com and Money Magazine. She can be reached at editor@ycharts.com.